Density-functional plane-wave pseudopotential calculations were performed for C and Si self-interstitials in 3C-type material. Various initial ionic configurations were used in seeking the global total-energy minimum. These included tetragonal, split [100] and split [110] geometries. Neutral C interstitials were found to have several nearly degenerate total-energy minima configurations in split-interstitial geometries. The associated formation energies ranged from 6.3 to 6.7eV in stoichiometric material. The neutral Si interstitials had a clear single minimum total-energy configuration at the tetrahedral configuration with C nearest neighbors, and exhibited a formation energy of 6.0eV. The split interstitial in the [110] direction at the Si site, and the tetrahedral configuration with Si nearest neighbors, were metastable and had significantly higher formation energies. The calculations indicated that the C interstitial introduced deep levels into the band-gap. The Si interstitial at the tetrahedral site behaved like a shallow donor.

Self-Interstitials in 3C-SiC. J.M.Lento, L.Torpo, T.E.M.Staab, R.M.Nieminen: Journal of Physics - Condensed Matter, 2004, 16[7], 1053-60